The present invention relates to the reception of information signals in a moving vehicle and, more particularly, to the reception of audio or video information transmitted from different sites within a respective service area or areas, wherein the same information signal is transmitted by the transmitters using different frequency channels.
The most common form of receiving broadcast entertainment and/or informative audio and video programming is through the medium of AM and FM radio, and VHF and UHF television, broadcasting and receiving respectively, in which the audio and/or video materials received are precisely the materials which are being broadcast at the time of reception. In these well known real time audio and video transmitter/receiver systems, the recipient has no choice but to accept whatever entertainment or informative program materials are selected for transmission, along with any program supporting message materials such as commercials, announcements and other related messages which the broadcaster or originator chooses to include with the program materials.
A more recent medium for receiving informative materials, primarily in an alphanumeric format is, for example, a FM radio sideband system which broadcasts to dedicated portable devices or computers which are adapted with special FM receivers and software. The materials are transmitted in digital format, received, and stored in a memory for subsequent access by the user using menu driven software and generally are utilized by being displayed on a self contained visual screen or computer monitor in conventional alphanumeric format. Software provided with the program materials by the originator allows the user to scan the incoming materials and to transfer to memory or display the materials which meet the subscriber/user desired parameters.
The typical broadcast radio and television transmission systems of previous mention employ VHF bands I, II, III, and the UHF bands IV and V and can supply other information signals in addition to the primary entertainment material. The information signals are intercepted by specialized receivers designed for that particular application. The signals are time division multiplexed (TDM) during the non-picture periods of a television signal or frequency division multiplexed (FDM) with transmitted FM radio signals. These supplementary signals usually are sent from one transmitter to a multitude of fixed receiving sites located entirely within the service area of the transmitter, wherein a service area is the area surrounding a transmitter over which the respective signal is radiated and may be faithfully received. It follows that the information signals can be received in a moving vehicle only if the vehicle remains within the service area and the reception within the service area is not obstructed.
Another medium for receiving information is by wireless telephony of which the well known cellular phone system is the most common application. In this medium, the telephone user not only receives information but also sends information in real time and the telephone may be mobile and thus useable to receive and send in and from a moveable vehicle. To be effective such a system is a two-way system operating in real time. That is, the user transmits information as well as receives information. The loss of some information is not critical since any lost conversation may be readily repeated, unlike a non-real time system wherein information may be stored for later use.
In a recently developing field, audio and video entertainment and/or informative information is transmitted and received in unique fashion by selectively delivering the information in real time to a multitude of receivers for storage. The stored information subsequently is retrieved by a user at his or her convenience in non-real time. Such a unique entertainment system is described for example in the U.S. Pat. No. 5,406,626 issued Apr. 11, 1995 and U.S. Pat. No. 5,524,051 issued Jun. 4, 1996, and U.S. Pat. No. 5,590,195 issued Dec. 31, 1996 in the U.S. application Ser. No. 08/627,947 filed Apr. 3, 1996 now U.S. Pat. No. 5,809,472 issued Sep. 15, 1998, and Ser. No. 08/664,290 filed Jun. 11, 1996 now U.S. Pat. No. 5,815,671 issued Sep. 29 1998, the contents of which are incorporated by reference herein.
Such a unique entertainment programming system particularly is adaptable for use with moving vehicles, that is, with receivers located in moveable vehicles, wherein the user or driver in the vehicle may access the stored entertainment or informative information at a convenient time. However, as mentioned above, the mobile receivers must have access to the transmitted information regardless of the extent of travel of the respective vehicles.
It follows therefore, that in such mobile reception applications, diverse transmission of the information signals is necessary to guarantee reception within each and every service area. If the signal from one transmitter is lost, the receiver must automatically search for another transmission source by scanning every channel within the frequency band until one is found carrying the same information signals. As the number of possible channels is large, it could take a long time for the receiver to search for the next available channel, during which time much information is lost. In addition, if there are multiple sources available, the receiver usually will accept the first signal transmission found regardless of whether it is the optimum transmission for the location of the receiver.
Accordingly, in the unique information/entertainment programming system of last mention, it would be highly desirable to provide a diverse multiple transmitter network and associated transmitter locating system whereby uninterrupted information signals may be received by a receiver in a moving vehicle while the vehicle is traveling within a service area or across a boundary into other service areas.